Dispensing Apparatus and Valve Means

ABSTRACT

According to the invention, there is provided a valve, and also dispensing or dosing apparatus ( 1 ) incorporating such a valve, for dispensing a predetermined dose of a first liquid into a second liquid, the apparatus comprising a sealed reservoir ( 10 ) for holding the first liquid, a reservoir outlet tube ( 24 ) connected to the reservoir at its in use upper region ( 18 ) and in fluid communication therewith, first valve means ( 30 ) for selectively dispensing a dose of the first liquid from the reservoir into the second liquid, and a dosing tube ( 26 ) between the reservoir outlet tube and the valve means. The apparatus is operable, when the reservoir holds the first liquid and on raising the level of the second liquid relative to the reservoir so as to subject the reservoir and first valve means to increased hydrostatic pressure, to discharge a dose of the first liquid into the dosing tube, via the reservoir outlet tube, and form a column of said first liquid that acts on the valve means, and subsequent lowering of the level of the second liquid relative to the apparatus so as to reduce the hydrostatic pressure acting on the reservoir and valve means causes the valve means to deliver the dose by opening of the valve means to allow dosing of the second liquid with the dose of the first liquid as the hydrostatic pressure acting on the valve means from the second liquid decreases below a predetermined amount.

FIELD OF THE INVENTION

This invention relates to a dispensing apparatus for delivering a dose of a first liquid into a second liquid, for example for delivering a dose of liquid additive into a lavatory cistern, and two valve means suitable for use of such a dispensing apparatus.

BACKGROUND OF THE INVENTION

It is known to dispense additives such as disinfectants and fragrances into a lavatory cistern in order to clean a lavatory as it is flushed. This may be done by placing a block containing soluble substances such as surfactants, disinfectants or fragrances concentrated form in the cistern which gradually dissolves to provide the active ingredient(s) into the water. A disadvantage of this is that, depending on the time between flushes, the amount of active ingredient dispensed will change. Further, as the block progressively dissolves, the rate of which the active ingredient is dispensed may change. It is also known to provide a dispensing unit which can dispense a predetermined dose into a toilet cistern as it is being flushed. Such a cistern works by including a valve which is held close by hydrostatic pressure of water in the cistern but is opened as the water level, and thus hydrostatic pressure, reduces as the water flushes out of the cistern. As the valve opens, a predetermined dose of active ingredient is dispensed. However, such systems may have air pockets trapped in a reservoir in which the active ingredient is kept, which may affect the dosage provided in each flush. Further, such systems can only be discharge active ingredients from a single reservoir.

The present invention seeks to overcome or ameliorate at least one disadvantage associated with the prior art.

While the dispensing apparatus of the invention has been devised as particularly suitable to be used in a toilet cistern, it will be apparent to a person skilled in the art that it is suitable for other applications in which it is required to dispense a dose of a first liquid into a second liquid.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided dispensing or dosing apparatus for dispensing a predetermined dose of a first liquid into a second liquid, the apparatus comprising a sealed reservoir for holding the first liquid, a reservoir outlet tube connected to the reservoir at its in use upper region and in fluid communication therewith, first valve means for selectively dispensing a dose of the first liquid from the reservoir into the second liquid, and a dosing tube between the reservoir outlet tube and the valve means. The apparatus is operable, when the reservoir holds the first liquid and on raising the level of the second liquid relative to the reservoir so as to subject the reservoir and first valve means to increased hydrostatic pressure, to discharge a dose of the first liquid into the dosing tube, via the reservoir outlet tube, and form a column of said first liquid that acts on the valve means, and subsequent lowering of the level of the second liquid relative to the apparatus so as to reduce the hydrostatic pressure acting on the reservoir and valve means causes the valve means to deliver the dose by opening of the valve means to allow dosing of the second liquid with the dose of the first liquid as the hydrostatic pressure acting on the valve means from the second liquid decreases below a predetermined amount.

The term “liquid” is intended to encompass solutions, suspensions and gels etc.

Preferably, the reservoir of the dispensing apparatus has sides which are sloped from the reservoir outlet to the widest portion of the reservoir. This reduces the possibility of air being trapped as the level of the first liquid rises, which would interfere with the correct function of the dispensing system; in particular, could cause the dosage dispensed to vary. By providing the sloped sides, air is not trapped and thus the dose is made more consistent.

The slope of the sides may be constant, so further reducing the chances of air becoming trapped in the reservoir, as there are no changes in the slope by which air bubbles could get trapped. In one embodiment, the reservoir outlet tube is mounted at the uppermost point of the reservoir. Again, this may reduce the possibility of air becoming trapped in the reservoir and affecting the dosage dispensed. The reservoir outlet tube may extend at least partly in an in use upward direction from the in use uppermost point of the reservoir, which, again, allows air in the reservoir to easily be expelled along the outlet tube.

A vent chamber may be provided, which is connected between the reservoir outlet tube and the dosing tube. The vent chamber allows a dose from the reservoir to travel from the reservoir to the dosing tube, while allowing air in the apparatus to be expelled.

A plug or other seal may be provided at or adjacent to the outlet, for sealing the reservoir before its first use. The plug may be removable by depression of the reservoir outlet tube into the reservoir, Alternatively, other known methods may be employed to remove or break the plug to allow the first liquid to exit the reservoir.

In embodiments, a second reservoir may be provided, for holding a third liquid to be dispensed into the second liquid, together with a second valve means corresponding to the first valve means, for dispensing a dose of the third liquid from the second reservoir into the second liquid. This allows multiple active ingredients, which cannot be stored stably together, to be dispensed into the second liquid at the same time, The second reservoir may be connected to the second valve means via a second reservoir outlet tube and a second dosing tube. The diameter of the second dosing tube may be the same as, or different from, the diameter of the first dosing tube. Changing the diameter of the tube changes the dose provided in each cycle of lowering and rising of the level of the second liquid.

In embodiments of the invention, the reservoir may be formed as a collapsible member, and may be supported by a frame allowing communication of the second liquid inside and outside of the frame, for example by provision of communicating vents or holes in the frame. Further, the reservoir may comprise flexible corrugated sides which collapse as the reservoir is emptied. The reservoir may be cylindrical with a collapsible corrugated curved wall, wrapped around on itself and extending between the top and the base. The reservoir may collapse upwardly by being fixed to the frame at the top. This may provide improved expulsion of the air in the space above the first liquid during the dosing of the dosing tube, to facilitate better functioning of the dispensing apparatus. In particular, this reduces the possibility of air being trapped in the reservoir, which would reduce the dose of first liquid provided in a subsequent dispensing event. Further, as, in embodiments, the collapsible reservoir does not contact with the frame at its sides, there is reduced interference between the frame and the reservoir as it is drained by successive dosages being dispensed into the second liquid.

According to a second aspect of the invention, there is provided valve means for controlling flow of a first liquid, the valve means comprising first and second opposed flexible membrane parts with a closeable fluid channel formed therebetween, the valve means being operable such that, when attached to an inlet tube containing a column of a first liquid and immersed in a second liquid so as to subject the valve means to at least a minimum hydrostatic pressure, the hydrostatic pressure causes opposing faces of the membranes to close the fluid channel and prevent flow of the first liquid through the valve body, and, when a level of the second liquid is lowered relative to the valve means so as to reduce the hydrostatic pressure, the flexible membranes separate to open the fluid channel, so as to allow a flow of the first liquid through the valve body.

In embodiments, the membrane parts are joined to one another all around their margins to form the channel therebetween. This provides a sealed valve. In embodiments the fluid channel may be closed by the facing surfaces of the opposed membrane parts being pushed into mutual contact by the hydrostatic pressure of the second liquid. This provides a simple construction and operation of the valve as only the two membranes are required to form the valve.

An inlet and an outlet may be provided, which may be formed in the first opposed membrane part. As the inlet and outlet are not formed in a seal between the two membranes, more sensitive and controllable action of the valve can be obtained.

In embodiments, an outlet channel is provided, which is attached to the outlet of the valve means, an upstream end of the outlet channel in the direction flow of the first liquid being positioned lower when in use than a second, downstream end of the outlet channel, and an upper portion of the outlet channel between the upstream and downstream ends being positioned higher than both ends being used. Such an inverted “U” configuration means that air is trapped in the upper portion as the level of the second liquid rises from below the downstream end to above the level of the upper portion. This effectively provides an air lock between the valve and the second liquid, to provide good separation between any of the first liquid remaining in the outlet channel, and the second liquid.

In embodiments, the internal diameter of the outlet channel increases, in some cases suddenly, for example by the provision of a shoulder between the narrower and wider diameter portions, in a downstream direction at or adjacent the downstream end of the outlet channel. By doing this, in the enlarged diameter region, a significant volume of air can be trapped, which, as the level of the second liquid rises, converts into a longer column of air in the narrower upper portion. In this way, the height at the top of the upper portion above the downstream end can be reduced, whilst still providing a substantial column of air in the upper portion. Therefore, the relative height between the upstream and downstream ends of the channel can be increased.

In embodiments, the channel is directed downwards at its downstream end so as to face the surface of the second liquid as it rises from below to above the downstream end.

In embodiments, the end of the downstream end is tapered, or finished at an oblique angle, in use, to the plane of the second liquid. This ensures that the first liquid, when dispensed, is not retained in the outlet channel by the effects of surface tension, by effectively increasing the size of the downstream end opening and providing a point from which the first liquid can drip.

In embodiments, a second valve means may be provided. This may be provided by forming the second valve as a mirror image of the first valve about one of the membrane parts, there being three membrane parts in parallel, or sealed at their margins, the outer two membrane parts each having an inlet and an outlet, with the central membrane part acting as one side of each of the two valves. This provides a simple and easy construction of two valves for dispensing two different liquids into the second liquid.

In embodiments, the valve means of the second aspect may be incorporated into the dispensing apparatus of the first aspect.

In embodiments, when the valve means is immersed in the second liquid, in its intended orientation, the hydrostatic pressure acting to cause the flexible membranes to seal the valve is always greater than the hydrostatic pressure acting to force the second liquid into the valve body, and the second liquid is therefore prevented from entering the valve by sealing of the membranes, and also by the air lock in the outlet channel, where provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now described, purely by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a dispensing apparatus according to an embodiment of the invention;

FIG. 2 shows a reservoir according to an embodiment of the invention;

FIG. 3 shows a valve means according to an embodiment of the invention; and

FIG. 4 shows an alternative reservoir for a dispensing means for a dispensing apparatus according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The dispensing apparatus 1 comprises a polyethylene reservoir 10, a polypropylene vent chamber assembly 20, and a valve 30. The vent chamber assembly 20 consists of a vent chamber 22, a reservoir outlet tube 24, a dosing tube 26 and a breathing tube 28. The reservoir outlet tube 24 connects to the reservoir 10 with the vent chamber 22 the vent chamber 22 is vented via the breathing tube 28, allowing excess air to be expelled from the dispensing apparatus 1. The breathing tube 28 is formed with an inverted U-bend so that the free end of the tube points downwards to form an air lock as the level of a second liquid, in the present embodiment, water, rises so that it is prevented from entering the vent chamber 22.

The reservoir 10 contains a first liquid, in the present embodiment, fragranced surfactant solution, but could also contain other active ingredients, such as bleaching or descaling solution or non-active ingredients such as dye, or a combination of any two or more of such ingredients,

The reservoir 10 comprises a sachet formed from two flexible sheets, joined together at their margins by a welded seam to form a sealed enclosure. Each sheet is, in the present embodiment, formed with a generally rectangular portion 12 and a triangular portion 14 extending from the long end of the rectangle to a point. In this way, sides 16 of the reservoir 10 are sloped from the widest portion of the reservoir 10 to an apex 18, at which point the reservoir outlet tube 24 is positioned entering the reservoir 10 to allow liquid in the reservoir 10 to travel up the reservoir outlet tube 24 into the venting chamber 22. In the present embodiment, the sloping sides 16 are straight to reduce the possibility of air being trapped in the reservoir 10. In an embodiment, a plug 19 is formed at the apex 18 of the reservoir 10, which is displaced by the reservoir outlet tube 24 when it is inserted into the reservoir 10.

Looking now at FIG. 3, this shows the valve 30 in detail. The valve 30 comprises a first and second membrane 32, 34 which are welded together at their margin with a welded seam. The first membrane 32 includes an inlet 36 and an outlet 38, The outlet 38 is disposed in an in use orientation below the inlet 36. The membranes 32, 34 may be biased towards mutual contact. Alternatively, the membranes 32, 34 may be inherently unbiased. In any case, the membranes 32, 34 are arranged so that hydrostatic pressure from the second liquid surrounding the valve 30 and acting on the outer surfaces of the membranes 32, 34 is sufficient to push the membranes 32, 34 together and thus close the valve 30.

Referring again to FIG. 1, the figure shows that the inlet 36 of the valve 30 is connected to the dosing tube 26. The outlet 38 of the valve 30 is connected to an outlet channel 40. The outlet channel 40 comprises an upstream end 42 and a downstream end 44 as well as an upper portion 46 which is, in an in use orientation, disposed above both the upstream 42 and downstream 44 ends of the outlet channel 40.

The operation of a dispenser according to an embodiment of the invention, which has been suspended in a lavatory cistern (not shown) just above the bottom of the cistern will now be described during the course of a filling and flushing cycle.

First, the situation when the cistern has been flushed and is refilling will be discussed. As the water level rises relative to the dispenser 1, the reservoir 10 and valve 30 are subjected to hydrostatic pressure. The hydrostatic pressure acting on the reservoir 10 compresses the reservoir 10 and drives out any air that has been drawn into it. Air driven out of the reservoir 10 escapes up the reservoir supply tube 24, through the vent chamber 22 and out of the breathing tube 28. By the time the water level reaches the top of the reservoir 10, there is no air remaining in it, which is completely filled by the first liquid. As the water level rises above the top of the reservoir 10, the hydrostatic pressure acting on the reservoir 10 forces the solution out of it and into the reservoir supply tube 24.

The level of the solution rises in the reservoir supply tube 24 approximately in step with the water level in the cistern, the differences in the levels being determined by the density of the solution. When the level of the second liquid reaches the bottom of the vent chamber 22, the inlet and outlet channels 36, 38 of the valve 30 are filled with the first liquid from the previous flush and a small amount of the solution remains in the bottom of the dosing tube 26.

Any of the first liquid that enters the vent chamber 22 as the level of the second liquid rises in the cistern is drawn down grooves of the dosing tube 26 and a column of the solution forms very quickly in the dosing tube 26. The solution is drawn into the dosing tube 26 so quickly that the level of the solution in the vent chamber 22 rises very little until the dosing tube 26 is filled with the solution. Air displaced from the dosing tube 26 by the first liquid escapes up the centre of the dosing tube 26 as the first liquid is drawn down the internal surface of the dosing tube 26, through the vent chamber 22 and out of the breather tube 28.

Once the cistern has finished filling and the reservoir supply tube 24, vent chamber 22 and dosing tube 26 are filled with the first liquid, the level of the first liquid has risen to a level that is approximately equal to the level of the free end of the breather tube 28. The hydrostatic pressure of the water acting on the membranes 32, 34 of the valve 30 is equal to the hydrostatic pressure of the column of the solution in the dosing tube 26 acting on the membranes 32, 34, which therefore remain in close mutual engagement, preventing a flow of the solution from the inlet channel to the outlet channel 40.

During flushing of the cistern, once the water level in the cistern has fallen to the level of the solution in the breather tube 28, so as to expose the free end of the breather tube 28 to the air, the level of the solution in the breather tube 28, vent chamber 22, and reservoir supply tube 24 falls approximately apace with the water level in the cistern.

It can be seen that the level of the solution in the dosing tube 26 has not fallen, because although the hydrostatic pressure exerted by the column of the solution in the dosing tube 26 on the membranes 32, 34 of the valve 30 is greater than that exerted by the water on the membranes, a minimum difference of pressure is required to deform the membranes 32, 34 sufficiently to enable solution to flow between them and from the inlet channel 36 to the outlet channel 40.

Once the minimum required difference of pressure is obtained by means of the falling water level, the hydrostatic pressure exerted by the column of the first liquid in the dosing tube 26 deforms the membranes 32, 34 of the valve 30 sufficiently for the solution to flow from the inlet channel 36 of the valve 30 to the outlet channel 40 and into the cistern. The flow of the solution from the valve 30 continues until the hydrostatic pressure of the remaining column of the solution in the dosing tube 26 is insufficient to deform the membranes 32, 34, whereupon the membranes 32, 34 return to engagement with the valve body, interrupting the flow of the solution from the inlet channel of the valve 30 to the outlet channel 40.

It is important that the downstream end 44 of the outlet channel 40 is at a higher level than the upstream end 42 of the outlet channel 40. This difference in level ensures that, during the filling of the cistern, while the water level is above the valve 30 but below the vent chamber 22 and the solution has not yet started to flow into the dosing tube 26, the hydrostatic pressure acting on the membranes 32, 34 due to the water and tending to maintain the membranes 32, 34 in mutual engagement is always greater than the hydrostatic pressure acting at the upstream end 42 of the outlet channel 40 and tending to force water into the valve 30, so that water is prevented from entering the valve 30. The provision of an air column in the outlet channel 40 as the water level in the cistern rises from below the downstream end 44 of the outlet channel 40 to above the upper portion of the outlet channel 40 also forms a further valve 30 in the system; the air column effectively provides an air lock between the second liquid and the valve 30, which prevents any mixing of residual first liquid in the outlet channel 40 with the water in the cistern. This, in turn, ensures a uniform dose is given with each dispensing operation.

FIG. 4 shows an alternative arrangement for the reservoir 130 according to an embodiment of the present invention. In the embodiment, the reservoir 130 is not formed as a sachet, as described above, but instead is formed as a flexible, generally cylindrical reservoir (although other cross sectional shapes would also be possible), which, in use, is orientated with the cylindrical axis substantially vertical, and the sides of which are corrugated, to provide a concertina formation. The reservoir 130 is mounted in a frame 132, which has vents or holes 134 to allow fluid communication between the main volume of the liquid in which the dispenser is placed with the reservoir 130. The remainder of the dispenser is as described above. As the water level in the cistern in which the reservoir 130 is placed rises, the hydrostatic pressure on the reservoir 130 increases, in the same way as described above. However, in the present embodiment, the reservoir 130 collapses upwardly, so pushing any air which may be trapped in the reservoir 130 into the reservoir supply tube 124 and the first liquid upwards, so reducing the possibility that air trapped in the reservoir 130 may be included as part of the dose of first liquid, thus in effect reducing the actual dose of first liquid supplied into the dosing tube for dispensing into the second liquid. Further, in the present embodiment, the reservoir 130 is mounted on the frame 132 at the top, at or adjacent the reservoir supply tube 124. A space is formed laterally between the sides of the reservoir and the frame, so that the sides of the reservoir 130 do not touch the frame as it moves due to the varying hydrostatic pressure acting on it as the level of the second liquid in the cistern varies. Once again, the upper sides of the reservoir 130 are straight and sloped from the wider side portion of the reservoir 130 to the reservoir supply tube 124, thus reducing the possibility of air being trapped in the reservoir 130.

The present invention has been described purely by way of example, and various modifications, omissions and/or additions will be apparent to the person skilled in the art, all of which fall within the scope and spirit of the invention.

Reference to prior art in this application is not an acknowledgement that such prior art was well known at the time of filing this application, or that the disclosures of the prior art formed part of the common general knowledge.

Unless the context clearly requires otherwise, the terms “comprising”, “comprises” and the like are intended to be interpreted in the inclusive, rather than exhaustive sense, that is “including, but not limited to”. 

1. Dispensing apparatus for dispensing a predetermined dose of a first liquid into a second liquid, the apparatus comprising: a sealed reservoir for holding the first liquid; a reservoir outlet tube connected to the reservoir at its in use upper region and in fluid communication therewith; first valve means for selectively dispensing a dose of the first liquid from the reservoir into the second liquid; and a dosing tube between the reservoir outlet tube and the valve means, the apparatus being operable, when the reservoir holds the first liquid, and on raising the level of the second liquid relative to the reservoir so as to subject the reservoir and first valve means to increased hydrostatic pressure, to discharge a dose of the first liquid into the dosing tube, via the reservoir outlet tube, and form a column of the first liquid that acts on the valve means, and subsequent lowering of the level of the second liquid relative to the apparatus so as to reduce the hydrostatic pressure acting on the reservoir and valve means causes the valve means to deliver the dose by opening of the valve means to allow dosing of the second liquid with the dose of the first liquid as the hydrostatic pressure acting on the valve means from the second liquid decreases below a predetermined amount.
 2. Dispensing apparatus according to claim 1, the reservoir sides being sloped from the reservoir outlet to the widest portion of the reservoir.
 3. Dispensing apparatus according to claim 1 the slope being at a constant angle.
 4. Dispensing apparatus according to claim 2 (the reservoir outlet) being dove-tailed towards the outlet from the widest portion of the reservoir.
 5. Dispensing apparatus according to claim 3, wherein the reservoir outlet tube is mounted at the uppermost point of the reservoir.
 6. Dispensing apparatus according to claim 1, wherein the reservoir outlet tube extends at least partly in an in use upward direction from the in use uppermost point of the reservoir.
 7. Dispensing apparatus according to claim 1, further comprising a vent chamber connected between the reservoir outlet tube and the dosing tube, to allow a first liquid dose from the reservoir to travel from the reservoir to the dosing tube, while allowing air in the apparatus to be expelled.
 8. Dispensing apparatus according to claim 1, further comprising a plug at or adjacent to the outlet for sealing the reservoir before first use, the plug being removable by depression of the reservoir outlet tube into the reservoir.
 9. Dispensing apparatus according to claim 1, comprising a second reservoir, for holding a third liquid to be dispensed into the second liquid, and a second valve means, corresponding to the first valve means, for dispensing a dose of the third liquid from the second reservoir into the second liquid.
 10. Dispensing apparatus according to claim 1, wherein the reservoir is formed as a collapsible member
 11. Dispensing apparatus according to claim 10, wherein the reservoir is supported by a frame allowing communication of the second liquid inside and outside the frame.
 12. Dispensing apparatus according to claim 10, wherein the reservoir comprises flexible, corrugated sides, which collapse as the reservoir is emptied.
 13. Dispensing apparatus according to claim 10, wherein the reservoir collapses upwardly.
 14. Valve apparatus for controlling flow of a first liquid, the valve apparatus comprising: first and second opposed flexible membrane parts with a closable fluid channel formed therebetween, the valve apparatus being operable such that, when attached to an inlet tube containing a column of a first liquid and immersed in a second liquid so as to subject the valve apparatus to at least a minimum hydrostatic pressure, the hydrostatic pressure causes opposing faces of the membranes to close the fluid channel and prevent flow of the first liquid through the valve body, and, when a level of the second liquid is lowered relative to the valve apparatus so as to reduce the hydrostatic pressure, the flexible membranes separate to open the fluid channel, so as to allow a flow of the first liquid through the valve body.
 15. Valve apparatus according to claim 14, wherein the opposed membrane parts are joined to one another all around their margins to form the channel therebetween.
 16. Valve apparatus according to claim 14, wherein the fluid channel is closed by facing surfaces of the opposed membrane parts being pushed into mutual contact by the hydrostatic pressure of the second liquid.
 17. Valve apparatus according to claim 14, wherein the valve apparatus comprises an inlet and an outlet.
 18. Valve apparatus according to claim 14, wherein the inlet and outlet are formed in the first opposed membrane part.
 19. Valve apparatus according to claim 14, further comprising an outlet channel attached to the outlet of the valve apparatus, a first, upstream end of the outlet channel, in the direction of flow of the first liquid, being positioned lower, in an in use orientation, than a second, downstream end of the outlet channel, an upper portion of the outlet channel between the upstream and downstream ends being positioned higher than both the upstream and downstream ends.
 20. Valve apparatus according to claim 14, the upper portion being of sufficient length to trap an air column in the outlet channel between the first and second ends as the level of the second liquid rises from below the level of the second end to above the level of the upper portion.
 21. Valve apparatus according to claim 19, the internal diameter of the outlet channel increasing in a downstream direction, in a region downstream of the upper portion.
 22. Valve apparatus according to claim 14, the downstream end being formed with the channel directed downwards.
 23. Valve apparatus according to claim 22, with the end being tapered, arranged at an angle other than 90° to the channel at the downstream end.
 24. Valve apparatus according to claim 14, wherein a second valve apparatus is formed by a third flexible membrane part and the second membrane part, the third membrane part being arranged on an opposing side of the second membrane part to the first membrane part, a second closeable channel being formed therebetween.
 25. Valve apparatus according to claim 24, wherein the third membrane part is joined to the second membrane part all around their margins to form a closeable channel therebetween.
 26. Valve apparatus according to claim 24, wherein the second valve means also comprises an inlet and an outlet.
 27. Valve apparatus according to claim 24, wherein the inlet and outlet of the second valve apparatus are provided in the third membrane part. 28-32. (canceled) 